The present disclosure is generally directed to polyester synthesis processes and, more specifically, to processes for the enzymatic synthesis of polyester resins which may be utilized in the formation of toners, and in particular, emulsion aggregation toners.
Electrophotographic printing utilizes toner particles which may be produced by a variety of processes. One such process includes an emulsion aggregation (“EA”) process that forms toner particles in which surfactants are used in forming a latex emulsion. See, for example, U.S. Pat. No. 6,120,967, the disclosure of which is hereby incorporated by reference in its entirety, as one example of such a process.
Combinations of amorphous and crystalline polyesters may be used in the EA process. This resin combination provides toners with high gloss and relatively low-melting point characteristics (sometimes referred to as low-melt, ultra low melt, or ULM), which allows for more energy efficient and faster printing. Poor crystalline-amorphous polymer combinations may result in toners that either do not show low-melt behavior or exhibit unacceptable heat cohesion properties. Low-melt polyester toners may thus rely upon a sharp-melting crystalline resin component to provide the low-melt behavior.
Crystalline polyesters may be prepared by the polycondensation of linear, aliphatic diacids and diols present in the polymer at a 1:1 molar ratio. The range of compatibility for crystalline materials with the amorphous components of a low-melt polyester toner may be very narrow; crystalline polymers that fall outside of this range give toners with either no low-melt properties or excessive temperature instability. Even slight modifications to the chemical structure of a crystalline polyester, such as the extension of either the diacid or the diol unit by one carbon atom, can result in dramatic changes to the polyester's solubility and thermodynamic properties, including its melting properties, and render it useless for a low-melt polyester toner. Moreover, these polyester resins have been synthesized by high-temperature polycondensation using metal catalysts. The presence of these catalysts in the final toner, combined with the energy required for polycondensation, represent environmental challenges. Therefore, there is a continual need for improving polyester resins synthesis. It is further desired to produce a toner with low gloss. In addition, it is desired to produce a toner that can be used in cold pressure fusing.